Retinal Vascular Abnormalities and Microglia Activation in Mice with Deficiency in Cytochrome P450 46A1-Mediated Cholesterol Removal

Am J Pathol. 2019 Feb;189(2):405-425. doi: 10.1016/j.ajpath.2018.10.013. Epub 2018 Nov 16.

Abstract

CYP46A1 is the cytochrome P450 enzyme that converts cholesterol to 24-hydroxycholesterol, a cholesterol elimination product and a potent liver X receptor (LXR) ligand. We conducted retinal characterizations of Cyp46a1-/- mice that had normal fasting blood glucose levels but up to a 1.8-fold increase in retinal cholesterol. The retina of Cyp46a1-/- mice exhibited venous beading and tortuosity, microglia/macrophage activation, and increased vascular permeability, features commonly associated with diabetic retinopathy. The expression of Lxrα and Lxrβ was increased in both the whole Cyp46a1-/- retina and retinal macroglia/macrophages. The LXR-target genes were affected as well, primarily in activated microglial cells and macrophages. In the latter, the LXR-transactivated genes (Abca1, Abcg1, Apod, Apoe, Mylip, and Arg2) were up-regulated; similarly, there was an up-regulation of the LXR-transrepressed genes (Ccl2, Ptgs2, Cxcl1, Il1b, Il6, Nos2, and Tnfa). For comparison, gene expression was investigated in bone marrow-derived macrophages from Cyp46a1-/- mice as well as retinal and bone marrow-derived macrophages from Cyp27a1-/- and Cyp27a1-/-Cyp46a1-/- mice. CYP46A1 expression was detected in retinal endothelial cells, and this expression was increased in the proinflammatory environment. Retinal Cyp46a1-/- phosphoproteome revealed altered phosphorylation of 30 different proteins, including tight junction protein zonula occludens 1 and aquaporin 4. Collectively, the data obtained establish metabolic and regulatory significance of CYP46A1 for the retina and suggest pharmacologic activation of CYP46A1 as a potential therapeutic approach to dyslipidemia-induced retinal damage.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cholesterol / genetics
  • Cholesterol / metabolism*
  • Cholesterol 24-Hydroxylase / deficiency*
  • Diabetes Mellitus, Experimental* / enzymology
  • Diabetes Mellitus, Experimental* / genetics
  • Diabetes Mellitus, Experimental* / pathology
  • Diabetic Retinopathy* / enzymology
  • Diabetic Retinopathy* / genetics
  • Diabetic Retinopathy* / pathology
  • Eye Proteins* / genetics
  • Eye Proteins* / metabolism
  • Gene Expression Regulation
  • Liver X Receptors / genetics
  • Liver X Receptors / metabolism
  • Mice
  • Mice, Knockout
  • Microglia* / enzymology
  • Microglia* / pathology
  • Retina* / enzymology
  • Retina* / pathology
  • Retinal Vessels* / abnormalities
  • Retinal Vessels* / metabolism

Substances

  • Eye Proteins
  • Liver X Receptors
  • Cholesterol
  • Cholesterol 24-Hydroxylase